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Fundamental Limits on Polarization Entanglement Distribution in Optical Fiber

Stefano Pirandola

Abstract

Characterizing the ultimate rates of entanglement distribution is essential for both foundational research and the practical deployment of quantum technologies. To investigate these limits, we introduce an erasure-Pauli channel model describing the distribution of polarization entanglement in optical fiber. For this channel, we derive bounds on the rates of entanglement distribution and related quantum resources under optimal local operations and two-way classical communication (two-way assisted capacities). This framework allows us to determine the optimal repeaterless performance achievable over realistic optical fibers affected by polarization mode dispersion, thereby providing a rigorous benchmark for long-distance polarization-based quantum communication. Finally, we show that both our model and capacity bounds remain robust under the inclusion of detector dark counts.

Fundamental Limits on Polarization Entanglement Distribution in Optical Fiber

Abstract

Characterizing the ultimate rates of entanglement distribution is essential for both foundational research and the practical deployment of quantum technologies. To investigate these limits, we introduce an erasure-Pauli channel model describing the distribution of polarization entanglement in optical fiber. For this channel, we derive bounds on the rates of entanglement distribution and related quantum resources under optimal local operations and two-way classical communication (two-way assisted capacities). This framework allows us to determine the optimal repeaterless performance achievable over realistic optical fibers affected by polarization mode dispersion, thereby providing a rigorous benchmark for long-distance polarization-based quantum communication. Finally, we show that both our model and capacity bounds remain robust under the inclusion of detector dark counts.
Paper Structure (6 sections, 17 equations, 2 figures)

This paper contains 6 sections, 17 equations, 2 figures.

Table of Contents

  1. Introduction
  2. Erasure-Pauli Channel
  3. Capacity bounds
  4. Polarization noise modelling
  5. Erasure-Pauli with dark counts
  6. Conclusions

Figures (2)

  • Figure 1: Schematic of an erasure-Pauli channel in panel (a) and an erasure-Pauli channel with dark counts in panel (b).
  • Figure 2: We plot the capacity $\mathcal{C}_2(\mathcal{E}_{{{\mathrm{EDH}}}})$ in ebits/use of the erasure-dephasing channel versus fiber distance in km (solid line). $\mathcal{E}_{{{\mathrm{EDH}}}}$ describes entanglement distribution in fiber with active polarization control (dephasing-dominated regime). We also plot an upper bound for $\mathcal{E}_{{{\mathrm{EDH}}}}^{{{\mathrm{dc}}}}$, which accounts for dark counts, with $p_{{{\mathrm{dc}}}}=10^{-2}$ (dashed line) and $p_{{{\mathrm{dc}}}}=10^{-3}$ (dotted line). Fiber parameters are: $\alpha=0.2$ dB/km, $\Delta \nu=100$ GHz and $D_{{{\mathrm{PMD}}}}=0.1$ ps/$\sqrt{{{\mathrm{km}}}}$.